Journal articles: 'Compounds Containing Polydentate Chelators'

1

Baral, Minati, B. K. Kanungo, and Peter Moore. "Synthesis of cis, cis-1,3,5-trisubstituted cyclohexane based chelators with polyfunctional pendant arms." Journal of Chemical Research 2005, no. 1 (January 2005): 43–45. http://dx.doi.org/10.3184/0308234053431149.

Full text

Abstract:

Some novel organic compounds of the type: cis, cis-1,3,5-tris(X)cyclohexane, where X= –CONH(CH2)2NH2, –CONH(CH2)3NH2, –CONH(CH2)2NCH –C6H4OH, CONH(CH2)3NCHC6H4OH, which are expected to function as potential polydentate chelators have been synthesised from 1,3,5-benzenetricarboxylic acid through multi-steps reactions. 1,3,5-benzenetricarboxylic acid was reduced to cis, cis-1,3,5-tris(ethylcarboxylate)cyclohexane, which on reaction with excess of 1,2-diaminoethane and 1,2-diaminopropane afforded two new compounds. Condensation of the obtained derivatives with three equivalents of salicylaldehyde resulted the formation of two new Schiff base compounds. All the compounds were characterised by a combination of elemental analysis, mass, IR, UV-Vis, 1H NMR and 13C NMR spectroscopy.

APA, Harvard, Vancouver, ISO, and other styles

2

Polivanova, A. G., I. N. Solovieva, D. O. Botev, D. Y. Yuriev, A. N. Mylnikova, and M. S. Oshchepkov. "Bifunctional gallium cation chelators." Fine Chemical Technologies 17, no. 2 (May 31, 2022): 107–30. http://dx.doi.org/10.32362/2410-6593-2022-17-2-107-130.

Full text

Abstract:

Objectives. The chemistry of 67Ga and 68Ga radionuclides plays a key role in nuclear medicine for applications in radiopharmaceuticals, in particular, in noninvasive in vivo molecular imaging techniques. The use of radiometals for labeling biomolecules typically requires the use of bifunctional chelators, which contain a functional group for covalent bonding with the targeting vector in addition to the polydentate fragment coordinating the metal. The aim of the present review article is to analyze the currently accumulated experimental material on the development and application of bifunctional chelators of gallium cations in medical research, as well as to identify the main requirements for the structure of the chelator and its complexes with 68Ga, which are used to create effective Gabased pharmaceutical preparations.Results. The review analyzed macrocyclic bifunctional chelators forming stable in vivo complexes with 68Ga and acyclic chelators, whose main advantage is faster complexation kinetics due to the short half-life of 68Ga. The advantages and disadvantages of both types of ligands were evaluated. In addition, a critical analysis of the binding constants and the conditions for the formation of complexes was presented. Examples of the influence of the geometry, lipophilicity, and total charge of the metal complex on the biodistribution of target radiopharmaceuticals were also given.Conclusions. Despite the progress made in the considered areas of bifunctional chelators, the problem of correlating the chemical structure of a metal-based radiopharmaceutical with its behavior in vivo remains important. Comparative studies of drugs having an identical targeting vector but containing different bifunctional chelating agents could help further elucidate the effectof metal chelate moiety on pharmacokinetics. In order to create effective bifunctional chelating agents, it is necessary to take into account such factors as the stability and inertness of the chelator and its complexes under physiological conditions, lipophilicity, complexation kinetics, chelation selectivity, combinatoriality of the basic structure, along with economic aspects, e.g., the availability of raw materials and the complexity of the synthesis scheme.

APA, Harvard, Vancouver, ISO, and other styles

3

Bogdanova, Irina, Dmitriy Andreev, Boris Skulin, Valentina Grabel'nyh, Nina Sosnovskaya, and Nikolay Korchevin. "THE USE OF POLYDENTATE CHALCOGEN-CONTAINING LIGANDS IN THE TECHNOLOGY OF BRILLIANT NICKEL PLATING." Modern Technologies and Scientific and Technological Progress 1, no. 1 (May 17, 2021): 17–18. http://dx.doi.org/10.36629/2686-9896-2021-1-1-17-18.

Full text

Abstract:

. Neutral chalcogen-containing polydentate compounds were used for the first time to obtain shiny nickel coatings from Watts electrolyte. The main technological parameters of electrolysis that ensure the production of the highest quality coatings are identified.

APA, Harvard, Vancouver, ISO, and other styles

4

Herrero, Santiago, and Miguel A. Usón. "Stereochemical nomenclature for octahedral coordination compounds containing polydentate ligands: a comprehensive proposal." Dalton Transactions, no. 37 (2008): 4993. http://dx.doi.org/10.1039/b806050a.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Egbers, Philipp H., Tilmann Harder, Boris P. Koch, and Jan Tebben. "Siderophore purification with titanium dioxide nanoparticle solid phase extraction." Analyst 145, no. 22 (2020): 7303–11. http://dx.doi.org/10.1039/d0an00949k.

Full text

Abstract:

The study of bacterial metal chelators, so called siderophores, requires robust analytical methods that selectively target and extract strong iron-binding compounds from complex samples containing a plethora of organic molecules.

APA, Harvard, Vancouver, ISO, and other styles

6

Raptopoulou, Catherine P. "Heterometallic Complexes Containing the NiII-LnIII-NiII Moiety—Structures and Magnetic Properties." Crystals 10, no. 12 (December 8, 2020): 1117. http://dx.doi.org/10.3390/cryst10121117.

Full text

Abstract:

This review summarizes the structural characteristics and magnetic properties of trinuclear complexes containing the NiII-LnIII-NiII moiety and also oligonuclear complexes and coordination polymers containing the same trinuclear moiety. The ligands used are mainly polydentate Schiff base ligands and reduced Schiff base ligands and, in some cases, oximato, β-diketonato, pyridyl ketone ligands and others. The compounds reported are restricted to those containing one, two and three oxygen atoms as bridges between the metal ions; examples of carboxylato and oximato bridging are also included due to structural similarity. The magnetic properties of the complexes range from ferro- to antiferromagnetic depending on the nature of the lanthanide ion.

APA, Harvard, Vancouver, ISO, and other styles

7

Zubenko, Anastasia D., Anna A. Shchukina, and Olga A. Fedorova. "Synthetic Approaches to the Bifunctional Chelators for Radionuclides Based On Pyridine-Containing Azacrown Compounds." Synthesis 52, no. 07 (December 16, 2019): 1087–95. http://dx.doi.org/10.1055/s-0039-1691540.

Full text

Abstract:

Synthetic ways to introduce functional groups (CO2Me, CO2H, OCH2CO2H, OCH2C≡CH, CH2OH, CH2Cl, CH2N3) into the pyridine ring of pyridine-containing azacrown compounds are described. These groups were introduced at position-4 of the pyridine ring, while keeping the macrocyclic carboxylate groups available for metal chelation. The derivatives were obtained by macrocyclization reaction of 4-substituted, trimethyl pyridine-2,4,6-tricarboxylate or by modification of methyl ester group in pyridine fragment of macrocycles. Obtained derivatives can be applied for preparing radiotherapeutic agents by conjugation to different vector biomolecules for targeted drug delivery to cancer cells without damaging healthy tissue.

APA, Harvard, Vancouver, ISO, and other styles

8

Lazarev, N., B. Petrov, A. Piskunov, P. Pochekutova, and V. Semenov. "Temperature Dependences of the Saturated Vapor Pressure of Tin (IV) Complexes with Polydentate Ligands." Bulletin of the South Ural State University series "Chemistry" 14, no. 1 (2022): 95–104. http://dx.doi.org/10.14529/chem220111.

Full text

Abstract:

The present paper is a continuation of the previously pursued studies of thermal properties of the Sn(IV) complexes with tridentate iminopyridine ligands. The study of thermal properties including temperature dependences of the saturated vapor pressure for Sn(IV) complexes with the tridentate iminopyridine ligands by differential scanning calorimetry (DSC) and the Knudsen effusion method leads to the use of the studied compounds as luminescent materials, as well as components for nonlinear optics. Coordination compounds of tin (IV) containing tridentate Schiff bases were chosen as objects of research: 2,4-di-tert-butyl-6-((phenyl (pyridin-2-yl)methylene)amino)phenolatotrichlorotin(IV) (1), 4-methyl-2-((phenyl (pyridin-2-yl)methylene)amino)phenolatotrichlorotin(IV) (2), 4-chloro-2-((phenyl (pyridin-2-yl)methylene)amino) phenolatotrichlorotin(IV) (3). These compounds were obtained by tem-plate synthesis from tin tetrachloride, various o-aminophenols, and α-carbonyl substituted pyri-dines; they contain an iminopyridine function and are capable of covalently binding to a metal by a phenolic group. Phase transitions of compounds 1–3 were studied by DSC in the temperature range 25–500 °C. For all studied complexes an endothermic transition correlated to melting was revealed. The melting points of the studied compounds were taken to be the temperature values corresponding to the onset of the transition, according to the standard Netzsch Software Proteus method: 300, 320 and 330 °C for 1–3, respectively. The temperature dependences of the saturated vapor pressure were obtained for the studied complexes, using the Knudsen effusion method with the weight recording of the amounts of sublimated substances. As a result of the experiments it was found that compounds 1–3 sublimated in the temperature ranges of 239–244, 228–260 and 226–256 °C, respectively. Thermodynamic parameters of sublimation processes were calculated.

APA, Harvard, Vancouver, ISO, and other styles

9

Gacesa, Ranko, Andrea A. P. Tripodi, Agostino Cilibrizzi, Antonella Leggio, Robert Hider, and Vincenzo Abbate. "Solid-Phase Synthesis and In-Silico Analysis of Iron-Binding Catecholato Chelators." International Journal of Molecular Sciences 21, no. 20 (October 12, 2020): 7498. http://dx.doi.org/10.3390/ijms21207498.

Full text

Abstract:

Siderophores are iron-complexing compounds synthesized by bacteria and fungi. They are low molecular weight compounds (500-1500 Daltons) possessing high affinity for iron(III). Since 1970 a large number of siderophores have been characterized, the majority using hydroxamate or catecholate as functional groups. The biosynthesis of siderophores is typically regulated by the iron levels of the environment where the organism is located. Because of their exclusive affinity and specificity for iron(III), natural siderophores and their synthetic derivatives have been exploited in the treatment of human iron-overload diseases, as both diagnostic and therapeutic agents. Here, solid-phase approach for the preparation of hexadentate, peptide-based tricatecholato containing peptides is described. The versatility of the synthetic method allows for the design of a common scaffolding structure whereby diverse ligands can be conjugated. With so many possibilities, a computational approach has been developed which will facilitate the identification of those peptides which are capable of providing a high affinity iron(III) binding site. This study reports an integrated computational/synthetic approach towards a rational development of peptide-based siderophores.

APA, Harvard, Vancouver, ISO, and other styles

10

Grim, Samuel O., Samuel A. Sangokoya, Ian J. Colquhoun, William McFarlane, and Raj K. Khanna. "Polydentate ligands containing phosphorus. 11. Synthesis of three new anionic tripod ligands, their neutral precursors, and related compounds." Inorganic Chemistry 25, no. 16 (July 1986): 2699–704. http://dx.doi.org/10.1021/ic00236a009.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Czégéni, Csilla Enikő, Ferenc Joó, Ágnes Kathó, and Gábor Papp. "Heterobimetallic Complexes of Bi- or Polydentate N-Heterocyclic Carbene Ligands and Their Catalytic Properties." Catalysts 13, no. 11 (November 5, 2023): 1417. http://dx.doi.org/10.3390/catal13111417.

Full text

Abstract:

This review summarizes developments in the synthesis and catalytic applications of those heterobimetallic carbene complexes in which at least two different metals are bound to the same ligand by at least one M-C(carbene) bond each. Several new synthetic methods for such complexes yielding well-defined and thoroughly characterized compounds are presented. The new complexes were found to be catalytically active in several (most often tandem) reactions. In certain cases, the incorporation of two different metals into the same imidazole- or triazol-based NHC-carbene complex resulted in the substantially higher catalytic activity of the heterobimetallic complex compared either to its homobimetallic analogs or to mixtures of comparable mononuclear complex fragments containing the two metals independently. This is a clear demonstration of advantageous metal–metal cooperation within the catalyst. Opposite examples are also discussed, where the heterobimetallic carbene complex proved inferior in relation to its homobimetallic analogs or to mixtures of homonuclear fragments.

APA, Harvard, Vancouver, ISO, and other styles

12

Tolouian, Ramin, Audrey Tolouian, Farzaneh Dastan, Vida Farhangi, Payam Peymani, Sanam Saeifar, Oscar Felipe Borja Montes, Leila Mohmoodnia, Mohammadreza Khosravifarsani, and Tella Sadighpour. "Antioxidants and cisplatin nephrotoxicity; an updated review on current knowledge." Journal of Nephropharmacology 12, no. 1 (October 30, 2022): e10556. http://dx.doi.org/10.34172/npj.2022.10556.

Full text

Abstract:

Cisplatin is a first-line antitumor drug which is applied in the therapeutic field of numerous kinds of cancers. The main dose-dependent adverse effect of cisplatin is nephrotoxicity in approximately one-third of patients, who received this drug during their treatment. Oxidative stress is one of the most significant mechanisms in cisplatin nephrotoxicity. Cisplatin-induced oxidative stress stimulates apoptosis, inflammation, mitochondrial damage within cells, and endoplasmic reticulum (ER) stress. The administration of an antioxidant in this context could be a suitable approach for preventing of cisplatin nephrotoxicity. Antioxidants are categorized into four classes: dietary antioxidants, free radical scavengers, thiol-containing compounds, and iron chelators.

APA, Harvard, Vancouver, ISO, and other styles

13

Klem-Marciniak, Ewelina, Marcin Biegun, Krystyna Hoffmann, and Józef Hoffmann. "Degree of complexation of microelement ions by biodegradable IDHA chelator in water and simulated fertilization environment." Polish Journal of Chemical Technology 25, no. 4 (December 1, 2023): 61–66. http://dx.doi.org/10.2478/pjct-2023-0039.

Full text

Abstract:

Abstract The degree of complexation of microelement ions by the biodegradable chelating agent - IDHA was examined in the work. The tests were carried out in water and in a simulated fertilizer environment. In order to compare the obtained results, tests were also carried out for the commonly used EDTA. The performed analyzes allow to determine the influence of the presence of compounds containing macroelements on the degree of binding of microelement ions by the biodegradable IDHA and EDTA chelators. The obtained results make it possible to determine the optimal conditions for the chelation of cations by IDHA, which in the future may be used in the production of micronutrient fertilizers on a large scale.

APA, Harvard, Vancouver, ISO, and other styles

14

Emregül, Kaan C., Ece Düzgün, and Orhan Atakol. "The application of some polydentate Schiff base compounds containing aminic nitrogens as corrosion inhibitors for mild steel in acidic media." Corrosion Science 48, no. 10 (October 2006): 3243–60. http://dx.doi.org/10.1016/j.corsci.2005.11.016.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Pospieszna-Markiewicz, Izabela, Marta A. Fik-Jaskółka, Zbigniew Hnatejko, Violetta Patroniak, and Maciej Kubicki. "Synthesis and Characterization of Lanthanide Metal Ion Complexes of New Polydentate Hydrazone Schiff Base Ligand." Molecules 27, no. 23 (December 1, 2022): 8390. http://dx.doi.org/10.3390/molecules27238390.

Full text

Abstract:

The new homodinuclear complexes of the general formula [Ln2L3(NO3)3] (where HL is newly synthesized 2-((2-(benzoxazol-2-yl)-2-methylhydrazono)methyl)phenol and Ln = Sm3+ (1), Eu3+ (2), Tb3+ (3a, 3b), Dy3+ (4), Ho3+ (5), Er3+ (6), Tm3+ (7), Yb3+ (8)), have been synthesized from the lanthanide(III) nitrates with the polydentate hydrazone Schiff base ligand. The flexibility of this unsymmetrical Schiff base ligand containing N2O binding moiety, attractive for lanthanide metal ions, allowed for a self-assembly of these complexes. The compounds were characterized by spectroscopic data (ESI-MS, IR, UV/Vis, luminescence) and by the X-ray structure determination of the single crystals, all of which appeared to be different solvents. The analytical data suggested 2:3 metal:ligand stoichiometry in these complexes, and this was further confirmed by the structural results. The metal cations are nine-coordinated, by nitrogen and oxygen donor atoms. The complexes are two-centered, with three oxygen atoms in bridging positions. There are two types of structures, differing by the sources of terminal (non-bridging) coordination centers (group A: two ligands, one nitro anion/one ligand, two nitro anions, group B: three ligands, three anions).

APA, Harvard, Vancouver, ISO, and other styles

16

Bredov, Nikolay S., Mikhail V. Gorlov, Andrey S. Esin, Anna A. Bykovskaya, Vyacheslav V. Kireev, Oksana A. Sinegribova, and Maria D. Ryabochenko. "Linear 2-Ethylhexyl Imidophosphoric Esters as Effective Rare-Earth Element Extractants." Applied Sciences 10, no. 4 (February 12, 2020): 1229. http://dx.doi.org/10.3390/app10041229.

Full text

Abstract:

Imidophosphoric organic esters containing phosphoryl groups are potential polydentate ligands and promising extractants of rare-earth elements. For their preparation, a monophosphazene salt [PCl3=N−PCl3]+[PCl6]− and short phosphazene oligomers of the general formula [Cl–(PCl2=N)n–PCl3]+[PCl6]−, where n = 4–7, were synthesized via living cationic polymerization of Cl3P=NSiMe3 and used as starting compounds. All phosphazenes were reacted with 2-ethylhexanol to obtain the corresponding esters of imidophosphoric acids (EIPAs). The formation of imidophosphoric acids occurs due to the phosphazene-phosphazane rearrangement of –P(OR)2=N– or –P(OH)(OR)=N– units, where R = 2-ethylhexyl. The prepared EIPAs were characterized by 1H, 31P NMR, and MALDI-TOF analyses and their extractive capacity towards lanthanide ions in aqueous solutions of nitric acid was examined. The EIPAs are mixtures of mono-, di-, and trifunctional compounds of the type HxA, where x = 1–3, which can form chelate complexes of lanthanide ions [Ln(A)z], where z = 3–6, depending on the chain length. The longer chain EIPAs are more suitable for collective rare-earth elements extraction. A comparison of the extraction properties of the EIPAs with the industrially used polyalkylphosphonitrilic acid (PAPNA) was drawn.

APA, Harvard, Vancouver, ISO, and other styles

17

Matveev, E. Yu, S. S. Novikov, V. Ya Levitskaya, A. I. Nichugovskiy, I. E. Sokolov, K. Yu Zhizhin, and N. T. Kuznetsov. "Interaction of the anion [2-B10H9O(CH2)4O]− with secondary amines." Fine Chemical Technologies 17, no. 5 (November 20, 2022): 427–38. http://dx.doi.org/10.32362/2410-6593-2022-17-5-427-438.

Full text

Abstract:

Objectives. One of the most promising methods of treating malignant tumors is 10B-neutron capture therapy. While compounds based on cluster boron anions [BnHn]2− (n = 10, 12) are often used as boron-containing agents due to the very high specific concentration of boron atoms per particle, the use of such compounds is associated with the need to develop new methods for the functionalization of boron clusters associated with the production of boron-containing derivatives containing biologically active functional groups. One of the most convenient methods of modification of [BnHn]2− (n = 10, 12) anions is the interaction of their derivatives containing cyclic oxonium-type substituents with negatively charged or neutral nucleophilic reagents. The disclosure of substituents of this type leads to the formation of closo-borates with functional groups separated from the cluster by an alkoxyl spacer chain. The purpose of this study is to develop methods for the synthesis of derivatives of the closo-decaborate anion [B10H10]2− with pendant nitrogen-containing groups.Methods. The general control of the reactions of the disclosure of cyclic substituents was carried out on the basis of 11B nuclear magnetic resonance (NMR) spectroscopy data. The structure of the obtained derivatives, including the nature of the attached functional groups, was determined using 1H, 13C attached proton test (APT) NMR and infrared (IR) spectroscopy data. The molecular weight of the synthesized compounds was confirmed by electrospray ionization mass-spectrometry (ESI–MS).Results. The interaction of the anion [2-B10H9O(CH2)4O]− with secondary amines (dimethylamine, dipropylamine, diallylamine, dibutylamine, diisobutylamine, morpholine, di-sec-butylamine) in an ethanol environment is investigated. As a result of the reactions, a cyclic substituent is shown to expand with the addition of a nucleophilic reagent. Seven new derivatives of the closodecaborate anion with pendant nitrogen-containing groups have been synthesized.Conclusions. A developed method for obtaining closo-decaborates with ammonium groups separated from the boron cluster by an alkoxyl spacer group is presented. It is shown that the use of amines of various structures does not fundamentally affect the course of the reactions, allowing the composition and structure of the target derivatives to be effectively regulated. The resulting compounds can be involved in further modification reactions due to a reactive pendant group, as well as being suitable for use as effective polydentate ligands. Closo-decaborates with pendant nitrogen-containing groups and their derivatives are of considerable interest in the synthesis of compounds for use in 10B-neutron capture therapy of malignant tumors.

APA, Harvard, Vancouver, ISO, and other styles

18

Pfaff, Annalise R., Justin Beltz, Emily King, and Nuran Ercal. "Medicinal Thiols: Current Status and New Perspectives." Mini-Reviews in Medicinal Chemistry 20, no. 6 (May 11, 2020): 513–29. http://dx.doi.org/10.2174/1389557519666191119144100.

Full text

Abstract:

The thiol (-SH) functional group is found in a number of drug compounds and confers a unique combination of useful properties. Thiol-containing drugs can reduce radicals and other toxic electrophiles, restore cellular thiol pools, and form stable complexes with heavy metals such as lead, arsenic, and copper. Thus, thiols can treat a variety of conditions by serving as radical scavengers, GSH prodrugs, or metal chelators. Many of the compounds discussed here have been in use for decades, yet continued exploration of their properties has yielded new understanding in recent years, which can be used to optimize their clinical application and provide insights into the development of new treatments. The purpose of this narrative review is to highlight the biochemistry of currently used thiol drugs within the context of developments reported in the last five years. More specifically, this review focuses on thiol drugs that represent the standard of care for their associated conditions, including N-acetylcysteine, 2,3-meso-dimercaptosuccinic acid, British anti-Lewisite, D-penicillamine, amifostine, and others. Reports of novel dosing regimens, delivery strategies, and clinical applications for these compounds were examined with an eye toward emerging approaches to address a wide range of medical conditions in the future.

APA, Harvard, Vancouver, ISO, and other styles

19

SAW, MAUNG MAUNG. "MEDICINAL RADIOPHARMACEUTICAL CHEMISTRY OF METAL RADIOPHARMACEUTICALS." COSMOS 08, no. 01 (June 2012): 11–81. http://dx.doi.org/10.1142/s0219607712300044.

Full text

Abstract:

Metal complexes have been used as medicinal compounds. Metals have advantageous features over organic compounds. Significant applications of metal complexes are in the field of nuclear medicine. Radiopharmaceuticals are drugs containing radioisotopes used for diagnostic and therapeutic purposes. The generalized targeting strategy for molecular imaging probe consists of three essential parts: (i) reporter unit or payload, (ii) carrier, and (iii) targeting system. Medicinal radiopharmaceutical chemistry pays special consideration to radioisotopes, as a reporter unit for diagnostic application or as a payload for therapeutic application. Targeting is achieved by a few approaches but the most common is the bifunctional chelator approach. While designing a radiopharmaceutical, a range of issues needs to be considered including properties of metal radioisotopes, bifunctional chelators, linkers, and targeting molecules. Designing radiopharmaceuticals requires consideration of two key words: "compounds of biological interest" and "fit for intended use." The ultimate goal is the development of new diagnostic methods and treatment. Diagnostic metal radiopharmaceuticals are used for SPECT and PET applications. Technetium chemistry constitutes a major portion of SPECT and gallium chemistry constitutes a major portion of PET. Therapeutic radiopharmaceuticals can be constructed by using alpha-, beta minus-, or Auger electron-emitting radiometals. Special uses of medicinal radiopharmaceuticals include internal radiation therapy, brachytherapy, immunoPET, radioimmunotherapy, and peptide receptor radionuclide imaging and therapy.

APA, Harvard, Vancouver, ISO, and other styles

20

Jiménez-Pulido, Sonia B., Francisco Hueso-Ureña, M. Paz Fernández-Liencres, Manuel Fernández-Gómez, and Miguel N. Moreno-Carretero. "Heteropolyhedral silver compounds containing the polydentate ligandN,N,O-E-[6-(hydroxyimino)ethyl]-1,3,7-trimethyllumazine. Preparation, spectral and XRD structural study and AIM calculations." Dalton Trans. 42, no. 2 (2013): 530–41. http://dx.doi.org/10.1039/c2dt32044d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Henriquez, Tania, Tom Baldow, Yat Kei Lo, Dina Weydert, Andreas Brachmann, and Heinrich Jung. "Involvement of MexS and MexEF-OprN in Resistance to Toxic Ion Chelators in Pseudomonas putida KT2440." Microorganisms 8, no. 11 (November 14, 2020): 1782. http://dx.doi.org/10.3390/microorganisms8111782.

Full text

Abstract:

Bacteria must be able to cope with harsh environments to survive. In Gram-negative bacteria like Pseudomonas species, resistance-nodulation-division (RND) transporters contribute to this task by pumping toxic compounds out of cells. Previously, we found that the RND system TtgABC of Pseudomonas putida KT2440 confers resistance to toxic metal chelators of the bipyridyl group. Here, we report that the incubation of a ttgB mutant in medium containing 2,2’-bipyridyl generated revertant strains able to grow in the presence of this compound. This trait was related to alterations in the pp_2827 locus (homolog of mexS in Pseudomonas aeruginosa). The deletion and complementation of pp_2827 confirmed the importance of the locus for the revertant phenotype. Furthermore, alteration in the pp_2827 locus stimulated expression of the mexEF-oprN operon encoding an RND efflux pump. Deletion and complementation of mexF confirmed that the latter system can compensate the growth defect of the ttgB mutant in the presence of 2,2’-bipyridyl. To our knowledge, this is the first report on a role of pp_2827 (mexS) in the regulation of mexEF-oprN in P. putida KT2440. The results expand the information about the significance of MexEF-OprN in the stress response of P. putida KT2440 and the mechanisms for coping with bipyridyl toxicity.

APA, Harvard, Vancouver, ISO, and other styles

22

Raymond, Onyekachi, William Henderson, Penelope J. Brothers, and Paul G. Plieger. "Coordination chemistry of Be2+ ions with chelating oxygen donor ligands: further insights using electrospray mass spectrometry." Zeitschrift für Naturforschung B 75, no. 5 (May 26, 2020): 473–82. http://dx.doi.org/10.1515/znb-2020-0005.

Full text

Abstract:

AbstractThe electrospray ionisation mass spectrometric (ESI-MS) behaviour of various complexes of beryllium have been investigated in the work described in this paper. These beryllium complexes were analysed in situ on a small scale by preparing appropriate molar mixtures of the Be2+ ion with ligands in a range of solvent systems. In view of the toxicity of beryllium compounds, this combinatorial type screening, involving miniscule amounts of material in solution, proved to be a safe strategy to pursue the coordination chemistry of beryllium. A variety of beryllium complexes were generated with various ligands in solutions and subjected to detailed characterisation by ESI-MS. These ligands, containing functional groups or architecture of interest, varied from simple ligands such as the acetate ion to more common beryllium chelators including hydroxy keto ligands (maltol, tropolone), malonic acid, chromotropic acid and citric acid. Generally, there was excellent correlation between the species observed in the mass spectrum and those confirmed to exist in solution by other techniques. This lent strong credence to the ESI-MS methodology used as an efficient analytical technique for the easy screening of a diverse range of potential ligands for the divalent beryllium ion.

APA, Harvard, Vancouver, ISO, and other styles

23

Kholin, Yuriy, and Vladimir Zaitsev. "Quantitative physicochemical analysis of equilibria on chemically modified silica surfaces." Pure and Applied Chemistry 80, no. 7 (January 1, 2008): 1561–92. http://dx.doi.org/10.1351/pac200880071561.

Full text

Abstract:

Quantitative physicochemical analysis (QPCA) enables the determination of the stoichiometric compositions and physicochemical parameters of species in equilibrium systems proceeding from the composition-property dependencies. The paper discusses modifications to the routine QPCA procedures required to characterize properties of reagents fixed on surfaces of silica-organic hybrid materials. The cooperative effects and the energetic heterogeneity of fixed reagents are especially important in this context. It follows that the main peculiarities of silica surfaces chemically modified by aliphatic amines are (a) the pronounced energetic heterogeneity of reagents caused by the non-random surface topography, (b) the decrease of the bacisity of amines induced by their interactions with residual surface silanols, and (c) the expressed sensibility of reactions in the near-surface layer to the state of its hydration. The interaction of grafted organic bases with metal ions results in the preferred formation of bis metal-ligand coordination compounds. Stability constants of complexes are decreased as a consequence of fixation and depend on not only donor but also acceptor ability of a solvent. Also, the denticity of polydentate ligands may decrease as a result of grafting. The changes of protolytic and complexing properties in the case of grafting of weak acids and phosphorus-containing complexons are due to their interactions with other surface groups and the influence of hydration effects in the near-surface layer.

APA, Harvard, Vancouver, ISO, and other styles

24

Sharma, Ankita, and Swaran Jeet Singh Flora. "Positive and Negative Regulation of Ferroptosis and Its Role in Maintaining Metabolic and Redox Homeostasis." Oxidative Medicine and Cellular Longevity 2021 (April 28, 2021): 1–13. http://dx.doi.org/10.1155/2021/9074206.

Full text

Abstract:

Ferroptosis is a recently recognized regulated form of cell death characterized by accumulation of lipid-based reactive oxygen species (ROS), particularly lipid hydroperoxides and loss of activity of the lipid repair enzyme glutathione peroxidase 4 (GPX4). This iron-dependent form of cell death is morphologically, biochemically, and also genetically discrete from other regulated cell death processes, which include autophagy, apoptosis, necrosis, and necroptosis. Ferroptosis is defined by three hallmarks, defined as the loss of lipid peroxide repair capacity by GPX4, the bioavailability of redox-active iron, and oxidation of polyunsaturated fatty acid- (PUFA-) containing phospholipids. Experimentally, it can be induced by many compounds (e.g., erastin, Ras-selective lethal small-molecule 3, and buthionine sulfoximine) and also can be pharmacologically inhibited by iron chelators (e.g., deferoxamine and deferoxamine mesylate) and lipid peroxidation inhibitors (e.g., ferrostatin and liproxstatin). The sensitivity of a cell towards ferroptotic cell death is tightly associated with the metabolism of amino acid, iron, and polyunsaturated fatty acid metabolism, and also with the biosynthesis of glutathione, phospholipids, NADPH, and coenzyme Q10. Ferroptosis sensitivity is also governed by many regulatory proteins, which also link ferroptosis to the function of key tumour suppressor pathways. In this review, we highlight the discovery of ferroptosis, the mechanism of ferroptosis regulation, and its association with other cellular metabolic processes.

APA, Harvard, Vancouver, ISO, and other styles

25

Coccia, EM, E. Stellacci, R. Orsatti, U. Testa, and A. Battistini. "Regulation of ferritin H-chain expression in differentiating Friend leukemia cells." Blood 86, no. 4 (August 15, 1995): 1570–79. http://dx.doi.org/10.1182/blood.v86.4.1570.bloodjournal8641570.

Full text

Abstract:

The mechanisms that regulate the expression of ferritin, the iron storage protein, have been investigated in Friend erythroleukemia cells (FLCs) induced to differentiate by several chemical compounds. In differentiating FLCs, administration of hemin increases the steady- state level of ferritin mRNA about 15-fold and the ferritin content about 20- to 25-fold. Conversely, iron salts have only mild stimulatory effects on these parameters and iron chelators only slightly inhibited the stimulatory effect of hemin. Transient transfection experiments with a construct in which the human ferritin H-chain promoter drives the expression of the indicator chloramphenicol acetyltransferase (CAT) gene show that the increase in mRNA content is mainly due to enhanced transcription. In addition to transcriptional effects, translational regulation resulting in the further increase in ferritin synthesis is shown by CAT assays from cells transiently transfected with a construct containing the coding region for the indicator CAT mRNA under the translational control of the mRNA ferritin iron-responsive element. We conclude that, in FLCs induced to differentiate, hemin acts synergistically with the differentiation inducers, increasing ferritin expression. Both transcriptional and translational mechanisms are responsible for this synergistic effect, which appears to be characteristic of differentiated erythroid cells because it is not observed in other cell types (ie, fibroblastic cell lines).

APA, Harvard, Vancouver, ISO, and other styles

26

Lehner, Sylvia M., Lea Atanasova, Nora K. N. Neumann, Rudolf Krska, Marc Lemmens, Irina S. Druzhinina, and Rainer Schuhmacher. "Isotope-Assisted Screening for Iron-Containing Metabolites Reveals a High Degree of Diversity among Known and Unknown Siderophores Produced by Trichoderma spp." Applied and Environmental Microbiology 79, no. 1 (October 12, 2012): 18–31. http://dx.doi.org/10.1128/aem.02339-12.

Full text

Abstract:

ABSTRACT Due to low iron availability under environmental conditions, many microorganisms excrete iron-chelating agents (siderophores) to cover their iron demands. A novel screening approach for the detection of siderophores using liquid chromatography coupled to high-resolution tandem mass spectrometry was developed to study the production of extracellular siderophores of 10 wild-type Trichoderma strains. For annotation of siderophores, an in-house library comprising 422 known microbial siderophores was established. After 96 h of cultivation, 18 different iron chelators were detected. Four of those (dimerum acid, fusigen, coprogen, and ferricrocin) were identified by measuring authentic standards. cis -Fusarinine, fusarinine A and B, and des-diserylglycylferrirhodin were annotated based on high-accuracy mass spectral analysis. In total, at least 10 novel iron-containing metabolites of the hydroxamate type were found. On average Trichoderma spp. produced 12 to 14 siderophores, with 6 common to all species tested. The highest number (15) of siderophores was detected for the most common environmental opportunistic and strongly fungicidic species, Trichoderma harzianum , which, however, did not have any unique compounds. The tropical species T. reesei had the most distinctive pattern, producing one unique siderophore ( cis -fusarinine) and three others that were present only in T. harzianum and not in other species. The diversity of siderophores did not directly correlate with the antifungal potential of the species tested. Our data suggest that the high diversity of siderophores produced by Trichoderma spp. might be the result of further modifications of the nonribosomal peptide synthetase (NRPS) products and not due to diverse NRPS-encoding genes.

APA, Harvard, Vancouver, ISO, and other styles

27

Grim, Samuel O., Patricia H. Smith, Suzanne Nittolo, Herman L. Ammon, Larry C. Satek, Samuel A. Sangokoya, Raj K. Khanna, Ian J. Colquhoun, William McFarlane, and James R. Holden. "Polydentate ligands containing phosphorus. 8. Coordination complexes of a new uninegative tridentate ligand, tris(diphenylthiophosphinoyl)methanide, and related compounds and the molecular structure of (bis(dimethylthiophosphinoyl)(diphenylthiophosphinoyl)methanido)chloromercury(II)." Inorganic Chemistry 24, no. 19 (September 1985): 2889–95. http://dx.doi.org/10.1021/ic00213a004.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Günther, Thomas, Nadine Holzleitner, Daniel Di Carlo, Nicole Urtz-Urban, Constantin Lapa, and Hans-Jürgen Wester. "Development of the First 18F-Labeled Radiohybrid-Based Minigastrin Derivative with High Target Affinity and Tumor Accumulation by Substitution of the Chelating Moiety." Pharmaceutics 15, no. 3 (March 3, 2023): 826. http://dx.doi.org/10.3390/pharmaceutics15030826.

Full text

Abstract:

In order to optimize elevated kidney retention of previously reported minigastrin derivatives, we substituted (R)-DOTAGA by DOTA in (R)-DOTAGA-rhCCK-16/-18. CCK-2R-mediated internalization and affinity of the new compounds were determined using AR42J cells. Biodistribution and µSPECT/CT imaging studies at 1 and 24 h p.i. were carried out in AR42J tumor-bearing CB17-SCID mice. Both DOTA-containing minigastrin analogs exhibited 3- to 5-fold better IC50 values than their (R)-DOTAGA-counterparts. natLu-labeled peptides revealed higher CCK-2R affinity than their natGa-labeled analogs. In vivo, tumor uptake at 24 h p.i. of the most affine compound, [19F]F-[177Lu]Lu-DOTA-rhCCK-18, was 1.5- and 13-fold higher compared to its (R)-DOTAGA derivative and the reference compound, [177Lu]Lu-DOTA-PP-F11N, respectively. However, activity levels in the kidneys were elevated as well. At 1 h p.i., tumor and kidney accumulation of [19F]F-[177Lu]Lu-DOTA-rhCCK-18 and [18F]F-[natLu]Lu-DOTA-rhCCK-18 was high. We could demonstrate that the choice of chelators and radiometals has a significant impact on CCK-2R affinity and thus tumor uptake of minigastrin analogs. While elevated kidney retention of [19F]F-[177Lu]Lu-DOTA-rhCCK-18 has to be further addressed with regard to radioligand therapy, its radiohybrid analog, [18F]F-[natLu]Lu-DOTA-rhCCK-18, might be ideal for positron emission tomography (PET) imaging due to its high tumor accumulation at 1 h p.i. and the attractive physical properties of fluorine-18.

APA, Harvard, Vancouver, ISO, and other styles

29

Kuznetsova, D. A., V. A. Rykova, and O. N. Podladchikova. "The Role of the Yersiniachelin Siderophore in the Physiology of Yersinia pestis." Problems of Particularly Dangerous Infections, no. 4 (February 12, 2023): 75–81. http://dx.doi.org/10.21055/0370-1069-2022-4-75-81.

Full text

Abstract:

Pathogenic bacteria use low-molecular-weight iron chelators – siderophores – to assimilate iron in the host body. Being recognized as virulence factors, these molecules, differing in structural and functional properties, are the subject of the most intensive research in medical microbiology. The present study is devoted to the investigation of yersiniachelin siderophore (Ych) found in the causative agent of plague, Yersinia pestis. The aim of the work was to clarify the role of Ych in the physiology of Y. pestis by comparing the properties of three strains of the plague microbe, differing in Ych production. Materials and methods. Three variants of Y. pestis EV76 strain were used in the experiments: parent strain Y. pestis EV76, its mutant that does not produce Ych due to deletion of three siderophore biosynthesis genes (analogues of ypo1530–1532 in Y. pestis CO92 strain) and a complemented mutant that was transformed by a recombinant pSC-A-5EV plasmid containing Ych biosynthesis genes cloned into the high-copy plasmid vector pSC-A-amp/kan. Comparative analysis of the three strains was carried out in terms of colony morphology, siderophore activity, growth rate, and sensitivity to hydrogen peroxide. Results and discussion. The comparison of these strains has revealed that the secretion of Ych by bacteria at 26 °С ensures the assimilation of iron. At 37 °С, Ych is not secreted into the medium and protects bacteria from the bactericidal action of reactive oxygen compounds. Thus, the study shows that yersiniachelin is able to stimulate the assimilation of iron by bacteria under iron-deficit conditions and has antioxidant properties.

APA, Harvard, Vancouver, ISO, and other styles

30

Lounissi, Sondès, Jean-François Capon, Frédéric Gloaguen, Fatma Matoussi, François Y. Pétillon, Philippe Schollhammer, and Jean Talarmin. "Reactivity of [Fe2(CO)6(μ-S2)] toward a Base-Containing Diphosphine (Ph2PCH2)2NCH3: Formation of Diiron Carbonyl Compounds Having Polydentate Heterofunctionalized Phosphine (PNS = Ph2PCH2N(CH3)CH2S) and Bidentate Thiophosphinito (Ph2PS = PS) Bridges." Organometallics 29, no. 5 (March 8, 2010): 1296–301. http://dx.doi.org/10.1021/om9011054.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Makhaeva, Galina F., Nadezhda V. Kovaleva, Elena V. Rudakova, Natalia P. Boltneva, Maria V. Grishchenko, Sofya V. Lushchekina, Tatiana Y. Astakhova, et al. "Conjugates of Tacrine and Salicylic Acid Derivatives as New Promising Multitarget Agents for Alzheimer’s Disease." International Journal of Molecular Sciences 24, no. 3 (January 24, 2023): 2285. http://dx.doi.org/10.3390/ijms24032285.

Full text

Abstract:

A series of previously synthesized conjugates of tacrine and salicylamide was extended by varying the structure of the salicylamide fragment and using salicylic aldehyde to synthesize salicylimine derivatives. The hybrids exhibited broad-spectrum biological activity. All new conjugates were potent inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with selectivity toward BChE. The structure of the salicylamide moiety exerted little effect on anticholinesterase activity, but AChE inhibition increased with spacer elongation. The most active conjugates were salicylimine derivatives: IC50 values of the lead compound 10c were 0.0826 µM (AChE) and 0.0156 µM (BChE), with weak inhibition of the off-target carboxylesterase. The hybrids were mixed-type reversible inhibitors of both cholinesterases and displayed dual binding to the catalytic and peripheral anionic sites of AChE in molecular docking, which, along with experimental results on propidium iodide displacement, suggested their potential to block AChE-induced β-amyloid aggregation. All conjugates inhibited Aβ42 self-aggregation in the thioflavin test, and inhibition increased with spacer elongation. Salicylimine 10c and salicylamide 5c with (CH2)8 spacers were the lead compounds for inhibiting Aβ42 self-aggregation, which was corroborated by molecular docking to Aβ42. ABTS•+-scavenging activity was highest for salicylamides 5a–c, intermediate for salicylimines 10a–c, low for F-containing salicylamides 7, and non-existent for methoxybenzoylamides 6 and difluoromethoxybenzoylamides 8. In the FRAP antioxidant (AO) assay, the test compounds displayed little or no activity. Quantum chemical analysis and molecular dynamics (MD) simulations with QM/MM potentials explained the AO structure–activity relationships. All conjugates were effective chelators of Cu2+, Fe2+, and Zn2+, with molar compound/metal (Cu2+) ratios of 2:1 (5b) and ~1:1 (10b). Conjugates exerted comparable or lower cytotoxicity than tacrine on mouse hepatocytes and had favorable predicted intestinal absorption and blood-brain barrier permeability. The overall results indicate that the synthesized conjugates are promising new multifunctional agents for the potential treatment of AD.

APA, Harvard, Vancouver, ISO, and other styles

32

Borovyk, Polina, Mariia Litvinchuk, Anton Bentya, Svitlana Orysyk, Yurii Zborovskiy, and Nataliia Slyvka. "Zn(II) and Ag(I) complexes of N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids and products their proton- and iodocyclization." Ukrainian Chemistry Journal 85, no. 3 (June 7, 2019): 3–19. http://dx.doi.org/10.33609/0041-6045.85.3.2019.3-19.

Full text

Abstract:

The possibility of using N-allylcarbothioamide derivatives as well as products of their iodine- and proton-initiated electrophilic heterocyclizations as chelating agents in complexation reactions with Zn(II) and Ag(I) ions is shown. Processing of the obtained experimental data showed that N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids H2L1 – H2L3 and their proton- and iodo-cyclization products HL4, HL5 containing four nucleophilic reaction centers (two oxygen atoms of the carbonyl and hydroxyl groups and N-, S-carbothioamide groups or N-atoms of the dihydrothiazole moiety) are polydentate ligands capable of coordinating with metal ions to form stable six-membered chelate metallocycles. A series of new chelating mono-, bi- and polynuclear complexes Zn(II) and Ag (I) of the composition [Zn2L1,32]n, [Zn2(HL1-3)2(CH3COO)2], [Ag2(HL1,3)2]n, [Zn(HL1-3)2], [Ag(H2L3)2NO3], [Zn(HL4,5)2], K[Ag(HL4,5)2] were synthesized and isolated in solid state. Their molecular structure was established by methods of elemental chemical analysis, NMR 1H, IR and UV-Vis spectroscopy. At a ratio of M:L 1:2, complexes were isolated in which two ligand molecules H2L1 − H2L3 are coordinated to the metal ion by the sulfur atoms of the carbothioamide group and the oxygen of the mono-deprotonated hydroxyl group. It was established that the products of the proton-/iodocyclization HL4, HL5 in the complex formation pass into the thione tautomeric form with coordination through the oxygen atoms of the deprotonated hydroxyl group and nitrogen atoms of the dihydrothiazole heterocycle. At M:L 1:1, binuclear or polynuclear coordination compounds are formed. It was shown that polymerisation in complexes [Zn2L1,32]n and [Ag2(HL1,3)2]n is due to the formation of Zn−(O2SN)−Zn and Ag−O−Ag polymer chains. Investigation of the solubility of the resulting complexes showed that the polymer complexes are weakly soluble or insoluble in DMSO, DMF, while the mononuclear are soluble in methanol, as well as in water.

APA, Harvard, Vancouver, ISO, and other styles

33

Borovyk, Polina, Mariia Litvinchuk, Anton Bentya, Svitlana Orysyk, Yurii Zborovskiy, and Nataliia Slyvka. "Zn(II) and Ag(I) complexes of N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids and products their proton- and iodocyclization." Ukrainian Chemistry Journal 85, no. 3 (June 7, 2019): 3–19. http://dx.doi.org/10.33609/6045.85.3.2019.3-19.

Full text

Abstract:

The possibility of using N-allylcarbothioamide derivatives as well as products of their iodine- and proton-initiated electrophilic heterocyclizations as chelating agents in complexation reactions with Zn(II) and Ag(I) ions is shown. Processing of the obtained experimental data showed that N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids H2L1 – H2L3 and their proton- and iodo-cyclization products HL4, HL5 containing four nucleophilic reaction centers (two oxygen atoms of the carbonyl and hydroxyl groups and N-, S-carbothioamide groups or N-atoms of the dihydrothiazole moiety) are polydentate ligands capable of coordinating with metal ions to form stable six-membered chelate metallocycles. A series of new chelating mono-, bi- and polynuclear complexes Zn(II) and Ag (I) of the composition [Zn2L1,32]n, [Zn2(HL1-3)2(CH3COO)2], [Ag2(HL1,3)2]n, [Zn(HL1-3)2], [Ag(H2L3)2NO3], [Zn(HL4,5)2], K[Ag(HL4,5)2] were synthesized and isolated in solid state. Their molecular structure was established by methods of elemental chemical analysis, NMR 1H, IR and UV-Vis spectroscopy. At a ratio of M:L 1:2, complexes were isolated in which two ligand molecules H2L1 − H2L3 are coordinated to the metal ion by the sulfur atoms of the carbothioamide group and the oxygen of the mono-deprotonated hydroxyl group. It was established that the products of the proton-/iodocyclization HL4, HL5 in the complex formation pass into the thione tautomeric form with coordination through the oxygen atoms of the deprotonated hydroxyl group and nitrogen atoms of the dihydrothiazole heterocycle. At M:L 1:1, binuclear or polynuclear coordination compounds are formed. It was shown that polymerisation in complexes [Zn2L1,32]n and [Ag2(HL1,3)2]n is due to the formation of Zn−(O2SN)−Zn and Ag−O−Ag polymer chains. Investigation of the solubility of the resulting complexes showed that the polymer complexes are weakly soluble or insoluble in DMSO, DMF, while the mononuclear are soluble in methanol, as well as in water.

APA, Harvard, Vancouver, ISO, and other styles

34

Foster, Lisa-Anne Agiato. "Utilization and cell-surface binding of hemin byHistoplasma capsulatum." Canadian Journal of Microbiology 48, no. 5 (May 1, 2002): 437–42. http://dx.doi.org/10.1139/w02-037.

Full text

Abstract:

Histoplasma capsulatum, a dimorphic fungus capable of causing severe respiratory illness in immuno-compromised individuals, resides in macrophages during mammalian infection. Previous studies suggest that siderophore-mediated iron transport may be important for the acquisition of iron from transferrin while the organism resides in macrophages. However, iron is also present as hemin in the intracellular environment of the macrophage and may serve as a major source of iron during infection. Thus the ability of H. capsulatum to use hemin and heme-containing compounds was examined. Histoplasma capsulatum G217B was iron-starved by adding the iron chelator deferoxamine mesylate to the culture. The addition of 10 µM hemin in the presence of deferoxamine mesylate restored growth to the levels seen in the absence of the chelator. Histoplasma capsulatum was also cultivated in an iron-limited, chemically defined medium without the addition of chelators and it was determined that the organism could also use hemoglobin as a sole source of iron. The method of iron internalization from heme was examined by measuring hemin binding to the yeast-cell surface. The ability of H. capsulatum to bind hemin was related to the nutritional status of the cells. Cells grown under iron-limited conditions bound more heme to the cell surface than did cells grown in medium without chelator. Pretreatment of iron-starved cells with proteinase K eliminated the ability of the organism to bind hemin. Additionally, the pre-incubation of iron-starved H. capsulatum with hemin eliminated the ability of these cells to remove hemin from the solution, although pre-incubation of cells with the iron-free form of hemin, protoporphyrin IX, only modestly affected the ability of the organism to bind hemin. These results suggest that H. capsulatum uses hemin as a sole source of iron and that one mechanism of iron acquisition involves a cell-surface receptor for hemin.Key words: H. capsulatum, heme utilization, iron.

APA, Harvard, Vancouver, ISO, and other styles

35

Hager, Sonja, Walter Berger, Christian R. Kowol, Eva A. Enyedy, and Petra Heffeter. "Abstract 4901: The role of protein disulfide isomerase and copper in the paraptotic cell death of clinically investigated anticancer thiosemicarbazones." Cancer Research 83, no. 7_Supplement (April 4, 2023): 4901. http://dx.doi.org/10.1158/1538-7445.am2023-4901.

Full text

Abstract:

Abstract α-N-Heterocyclic thiosemicarbazones (TSCs) have long been investigated as anticancer compounds. Triapine is one of the best-known TSCs for anticancer therapy and is currently tested in a clinical phase III trial. To further improve the anticancer activity of TSCs, novel derivatives (such as DpC and COTI-2) have been developed and clinically investigated for their activity against solid tumors. These novel TSCs belong to a subclass (incl. the tetra-methylated Triapine derivative, Me2NNMe2) that are terminally disubstituted and demonstrated enhanced anticancer activity in vitro and in vivo. The improved activity of these TSCs correlated with their ability to form stable copper complexes as well as induce paraptosis, a form of programmed but caspase-independent cell death, that is characterized by the formation of vesicles originating from the endoplasmic reticulum (ER). However, the molecular events behind paraptosis induction are still not fully elucidated. Consequently, the aim of this study was to investigate the molecular signaling behind paraptosis as well as the reasons behind the induction of this quite unknown form of cell death by TSCs. A whole-genome gene expression analysis of cells treated with a terminally disubstituted TSC revealed an upregulation of thiol homeostasis-related genes, copper metabolism, and metallothionein genes as well as ER stress response genes. In addition, we found an upregulation of the copper-sensitive and thiol-containing protein disulfide isomerase (PDI), which was confirmed on protein level. In cell-free activity studies, PDI was indeed inhibited by terminally disubstituted TSCs, although only in form of their copper complexes. In agreement, removal of copper ions by specific chelators greatly reduced their anticancer activity as well as paraptotic potential in cell culture. This inhibition was hypothesized to be induced by a general disruption of the thiol redox homeostasis affecting also other responsive proteins and resulting in a more oxidative environment, especially in the ER. In confirmation, thiol-containing small molecules could reduce the compound’s anticancer activity in viability assays. Furthermore, glutathione as well as PDI were detected predominantly in their oxidized form in cells treated with terminally disubstituted TSCs. Consequently, terminally disubstituted TSCs, which are characterized by higher anticancer activity, induce paraptosis due to their high copper complex stability. The formation of the complex results in the interaction with thiol-containing proteins and subsequently in the disruption of the thiol-redox homeostasis, which leads to paraptotic cell death. Overall this work shed light on the paraptotic cell death and will be of interest for future clinical development of anticancer TSCs, as paraptosis is hypothesized to overcome apoptosis-resistance of cancer cells. Citation Format: Sonja Hager, Walter Berger, Christian R. Kowol, Eva A. Enyedy, Petra Heffeter. The role of protein disulfide isomerase and copper in the paraptotic cell death of clinically investigated anticancer thiosemicarbazones. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4901.

APA, Harvard, Vancouver, ISO, and other styles

36

Orysyk, Svitlana, Vasyl Pekhnyo, Viktor Orysyk, Yuri Zborovskii, Polina Borovyk, and Vovk Mykhailo. "FUNDAMENTAL ASPECTS OF THE COORDINATION CHEMISTRY OF TRANSITION METALS WITH FUNCTIONALLY SUBSTITUTED THIOAMIDES (PART 1)." Ukrainian Chemistry Journal 88, no. 2 (March 25, 2022): 85–115. http://dx.doi.org/10.33609/2708-129x.88.02.2022.85-115.

Full text

Abstract:

The influence of competitive coordination, a tautomeric form of functionally substituted thioamides, conditions of synthesis and nature of the metal on the course of the reaction and structure of mono-, bi, and polynuclear complexes of 3d, 4d-metals is considered based on results obtained in the Department of "Chemistry of Complex Compounds" of the V.I. Vernadsky Institute of General and Inorganic Chemistry NAS of Ukraine, together with the staff of the Department of “Chemistry of Heterocyclic Compounds” of the Institute of Organic Chemistry NAS of Ukraine. The influence of ligand denticity, as well as conditions of complex formation on the structure of obtained complexes and their polymorphic modifications, was studied based on the reaction of d-metals with functionally substituted N, S- and O, N, S-containing thioamides. In addition, it is proved the influence of tautomeric forms of thioamides on the stereochemistry of coordination polyhedra: it is found that the thionic tautomeric form promotes the transposition of thioureas, while the thiol form promotes its cis-position in the square-planar of a polyhedron of 3d, 4d-metals in the structure of complexes. However, it was found that the thion tautomeric form leads to the formation of octahedral, while the thiol form to the square-planar of coordination nodes in complexes of Cu(II) and Ni(II), which are characterized by a change in coordination polyhedra (from square-planar and tetrahedron to octahedron) that depending on the strength of the ligand field. It is obvious that this effect of tautomeric forms of thioamides is associated with the formation of a conjugate system of double bonds in their molecules. In this case, the transition of thioamide to thiol form depends on the pH and the nature of the organic solvent: in a weakly alkaline medium or polar organic solvent (pyridine, chloroform) there is a shift of equilibrium towards to the dominance of thiol tautomeric form. It was found that the thionic tautomeric form of thioamides (depending on pH and substituent composition) reacts with metal salts mainly in neutral form or in the monoanionic form, forming complexes of molecular or ionic nature, while thiol form reacts in the form of dianion, forming complexes preferably anionic type. Ionic compounds are usually soluble or sparingly soluble in water in low concentrations (10-3–10-5 mol/l), while compounds of the molecular type are soluble only in DMSO and DMF. It is shown that the stereoselective synthesis of various ligand complexes is carried out mainly in three ways: 1) by the interaction of the initial components in the corresponding stoichiometry. In this case, the vacancy in the metal environment is occupied by either the anions of the starting metal salt (Hal-, SO42-, NO3-, CH3COO-, etc.) or other organic molecules (triphenylphosphine, pyridine, etc.); 2) carrying out parallel reactions (hydrolysis and oxidation of thioureas), which lead to participation in the coordination of by-products of the reaction; 3) carrying out reactions with intraligand rearrangements, which leads to the cyclization of organic ligands and coordination of the products of their transformation to the central metal ion. However, it was found that hydrolysis / oxidation or intraligand cyclization of substituted polydentate thioamides can occur both under the action of synthesis conditions and under the action of complexing metals as promoters of organic reactions. It was found that depending on the temperature and time of interaction of the starting reagents, different polymorphic modifications of complexes (triclinic or monoclinic) are formed, which differ in packing density and the nature of intermolecular interactions. As a result, such polymorphic modifications have different solubilities in water, which is important for the controlled synthesis of appropriate structures and their practical application.

APA, Harvard, Vancouver, ISO, and other styles

37

Tanaka, Akihiro, Sotaro Kusumoto, Harue Umeno, Yang Kim, Masaaki Nakamura, and Shinya Hayami. "Synthesis, structure, and magnetic properties of cubane-type tetranuclear Ni(II) and Cu(II) complexes with amide-containing polydentate ligand." Chemistry Letters 53, no. 2 (February 2024). http://dx.doi.org/10.1093/chemle/upae022.

Full text

Abstract:

Abstract Synthesis, structure, and magnetic properties of a tetranuclear metal complex with a symmetrical polydentate ligand, trans-(±)-1,2-(2-hydroxy-3-methoxybenzamido)cyclohexane (H2L), were characterized. The complexes have tetranuclear cubane cores with the formulae [Ni4(L)2(μ3-OMe)4(CH3OH)4] (1) and [Cu4(L)2(μ3-OMe)4(CH3OH)2] (2), whose cluster units are each composed of chiral ligands [(R, R)- or (S, S)-L]. The magnetic properties of the two compounds were characterized by 1 being ferromagnetic and 2 being antiferromagnetic.

APA, Harvard, Vancouver, ISO, and other styles

38

Mladěnka, Přemysl, Monika Moravcová, Marcel Hrubša, Zuzana Lomozová, Maria Carmen Catapano, Roberta Argento, Eduard Jirkovský, Radim Kučera, and Laura Mercolini. "A complex methodological approach for the screening of efficient and safe cobalt chelators." Medicinal Chemistry 18 (October 6, 2022). http://dx.doi.org/10.2174/1871530322666221006144449.

Full text

Abstract:

Background:: Cobalt is an essential trace element, but it can also rarely cause cobalt toxicity due to its release from cobalt-containing medical devices. Currently, there are no approved selective cobalt chelators which would represent an optimal treatment modality. Objective:: This study aimed to develop a simple and complex methodological approach for screening potential cobalt chelators along with evaluating their potential toxicity. Methods:: Firstly, a simple spectrophotometric assay employing 1-nitroso-2-naphthol-3,6- disulfonic acid disodium salt (NNDSA) for screening cobalt chelation was standardized at a pathophysiologically relevant range of pH 4.5-7.5. Then, the suitability of the method was verified using four known metal chelators (EDTA, 8-hydroxyquinoline, chloroxine and nitroxoline). As cobalt can catalyse the Fenton reaction, the potential toxicity of cobalt-chelator complexes was also determined by employing a novel HPLC method with coulometric detection. The effect on erythrocyte haemolysis was tested as well. Results:: The NNDSA method had high sensitivity enabling the detection of 25-200 nM of cobalt ions depending on pH conditions. Measurements could be carried out on a wide range of wavelengths from 470 to 540 nm. All tested complexes of the selected chelators decreased the rate of the Fenton reaction. Interestingly, chloroxine mixed with cobalt ions caused a marked lysis of erythrocytes in contrast to the other compounds. Conclusion:: The described complex methodological approach could serve as a simple, yet precise tool for making an evaluation of novel, effective and safe cobalt chelators.

APA, Harvard, Vancouver, ISO, and other styles

39

Dat, Nguyen Tien, Tran Thi Thanh Van, Dao Thi Nhung, Cao Quoc Anh, Tran Thanh Hang, Vu Thi Thao, Victor Khrustalev, and Le Tuan Anh. "Trithiazacrown Ethers Containing Piperidine Heterocycle: Synthesis, Structural Characterization and Evaluation Of α‐Glucosidase Inhibitory Activity." ChemistrySelect 9, no. 3 (January 16, 2024). http://dx.doi.org/10.1002/slct.202303741.

Full text

Abstract:

AbstractNew derivatives of crown compounds were successfully prepared via multicomponent reactions of a thia‐podand, an β‐keto ester and ammonium acetate based on modifications of the Petrenko‐Kritschenko reaction. The structure of the synthesized compounds was identified by physical‐chemical methods of analysis including IR, NMR, HRMS, and single‐crystal X‐ray diffraction. In addition, an in vitro assay against the α‐glucosidase of synthetic compounds was first evaluated and showed positive results. The most active compound exhibited an IC50 value of 5.69±0.27 μM, which is 37 fold more potent than the standard drug of acarbose (IC50 208.42±4.68 μM). Furthermore, prediction of ADMET parameters revealed that almost all synthesized trithiacrown ether derivatives expressed drug‐like characteristics. Our results provide useful evidence that crown ether compounds are not only good chelators with metal ions but also scaffolds for developing lead candidates in the treatment of diabetic disease.

APA, Harvard, Vancouver, ISO, and other styles

40

GRIM, S. O., S. A. SANGOKOYA, I. J. COLQUHOUN, W. MCFARLANE, and R. K. KHANNA. "ChemInform Abstract: Polydentate Ligands Containing Phosphorus. Part II. Synthesis of Three New Anionic Tripod Ligands, Their Neutral Precursors, and Related Compounds." Chemischer Informationsdienst 17, no. 49 (December 9, 1986). http://dx.doi.org/10.1002/chin.198649236.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Chan, Derek C. K., Irene Guo, and Lori L. Burrows. "Forging New Antibiotic Combinations under Iron-Limiting Conditions." Antimicrobial Agents and Chemotherapy 64, no. 3 (January 6, 2020). http://dx.doi.org/10.1128/aac.01909-19.

Full text

Abstract:

ABSTRACT Pseudomonas aeruginosa is a multidrug-resistant nosocomial pathogen. We showed previously that thiostrepton (TS), a Gram-positive thiopeptide antibiotic, is imported via pyoverdine receptors and synergizes with iron chelator deferasirox (DSX) to inhibit the growth of P. aeruginosa and Acinetobacter baumannii clinical isolates. A small number of P. aeruginosa and A. baumannii isolates were resistant to the combination, prompting us to search for other compounds that could synergize with TS against those strains. From literature surveys, we selected 14 compounds reported to have iron-chelating activity, plus one iron analogue, and tested them for synergy with TS. Doxycycline (DOXY), ciclopirox olamine (CO), tropolone (TRO), clioquinol (CLI), and gallium nitrate (GN) synergized with TS. Individual compounds were bacteriostatic, but the combinations were bactericidal. Our spectrophotometric data and chrome azurol S agar assay confirmed that the chelators potentiate TS activity through iron sequestration rather than through their innate antimicrobial activities. A triple combination of TS plus DSX plus DOXY had the most potent activity against P. aeruginosa and A. baumannii isolates. One P. aeruginosa clinical isolate was resistant to the triple combination but susceptible to a triple combination containing higher concentrations of CLI, CO, or DOXY. All A. baumannii isolates were susceptible to the triple combinations. Our data reveal a diverse set of compounds with dual activity as antibacterial agents and TS adjuvants, allowing combinations to be tailored for resistant clinical isolates.

APA, Harvard, Vancouver, ISO, and other styles

42

GRIM, S. O., P. H. SMITH, S. NITTOLO, H. L. AMMON, L. C. SATEK, S. A. SANGOKOYA, R. K. KHANNA, I. J. COLQUHOUN, W. MCFARLANE, and J. R. HOLDEN. "ChemInform Abstract: POLYDENTATE LIGANDS CONTAINING PHOSPHORUS. 8. COORDINATION COMPLEXES OF A NEW W UNINEGATIVE TRIDENTATE LIGAND, TRIS(DIPHENYLTHIOPHOSPHINOYL)METHANIDE, AND RELATED COMPOUNDS AND THE MOLECULAR STRUCTURE OF (BIS(DIMETHYLTHIOPHOSPHINOYL)(." Chemischer Informationsdienst 16, no. 51 (December 24, 1985). http://dx.doi.org/10.1002/chin.198551252.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Zhan, Xiaori, Zhehao Chen, Rong Chen, and Chenjia Shen. "Environmental and Genetic Factors Involved in Plant Protection-Associated Secondary Metabolite Biosynthesis Pathways." Frontiers in Plant Science 13 (April 8, 2022). http://dx.doi.org/10.3389/fpls.2022.877304.

Full text

Abstract:

Plant specialized metabolites (PSMs) play essential roles in the adaptation to harsh environments and function in plant defense responses. PSMs act as key components of defense-related signaling pathways and trigger the extensive expression of defense-related genes. In addition, PSMs serve as antioxidants, participating in the scavenging of rapidly rising reactive oxygen species, and as chelators, participating in the chelation of toxins under stress conditions. PSMs include nitrogen-containing chemical compounds, terpenoids/isoprenoids, and phenolics. Each category of secondary metabolites has a specific biosynthetic pathway, including precursors, intermediates, and end products. The basic biosynthetic pathways of representative PSMs are summarized, providing potential target enzymes of stress-mediated regulation and responses. Multiple metabolic pathways share the same origin, and the common enzymes are frequently to be the targets of metabolic regulation. Most biosynthetic pathways are controlled by different environmental and genetic factors. Here, we summarized the effects of environmental factors, including abiotic and biotic stresses, on PSM biosynthesis in various plants. We also discuss the positive and negative transcription factors involved in various PSM biosynthetic pathways. The potential target genes of the stress-related transcription factors were also summarized. We further found that the downstream targets of these Transcription factors (TFs) are frequently enriched in the synthesis pathway of precursors, suggesting an effective role of precursors in enhancing of terminal products. The present review provides valuable insights regarding screening targets and regulators involved in PSM-mediated plant protection in non-model plants.

APA, Harvard, Vancouver, ISO, and other styles

44

McDonagh, Anthony W., Brooke L. McNeil, Julie Rousseau, Ryan J. Roberts, Helen Merkens, Hua Yang, François Bénard, and Caterina F. Ramogida. "Development of a multi faceted platform containing a tetrazine, fluorophore and chelator: synthesis, characterization, radiolabeling, and immuno-SPECT imaging." EJNMMI Radiopharmacy and Chemistry 7, no. 1 (June 6, 2022). http://dx.doi.org/10.1186/s41181-022-00164-1.

Full text

Abstract:

Abstract Background Combining optical (fluorescence) imaging with nuclear imaging has the potential to offer a powerful tool in personal health care, where nuclear imaging offers in vivo functional whole-body visualization, and the fluorescence modality may be used for image-guided tumor resection. Varying chemical strategies have been exploited to fuse both modalities into one molecular entity. When radiometals are employed in nuclear imaging, a chelator is typically inserted into the molecule to facilitate radiolabeling; the availability of the chelator further expands the potential use of these platforms for targeted radionuclide therapy if a therapeutic radiometal is employed. Herein, a novel mixed modality scaffold which contains a tetrazine (Tz)––for biomolecule conjugation, fluorophore—for optical imaging, and chelator—for radiometal incorporation, in one construct is presented. The novel platform was characterized for its fluorescence properties, radiolabeled with single-photon emission computed tomography (SPECT) isotope indium-111 (111In3+) and therapeutic alpha emitter actinium-225 (225Ac3+). Both radiolabels were conjugated in vitro to trans-cyclooctene (TCO)-modified trastuzumab; biodistribution and immuno-SPECT imaging of the former conjugate was assessed. Results Key to the success of the platform synthesis was incorporation of a 4,4′-dicyano-BODIPY fluorophore. The route gives access to an advanced intermediate where final chelator-incorporated compounds can be easily accessed in one step prior to radiolabeling or biomolecule conjugation. The DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) conjugate was prepared, displayed good fluorescence properties, and was successfully radiolabeled with 111In & 225Ac in high radiochemical yield. Both complexes were then separately conjugated in vitro to TCO modified trastuzumab through an inverse electron demand Diels–Alder (IEDDA) reaction with the Tz. Pilot small animal in vivo immuno-SPECT imaging with [111In]In-DO3A-BODIPY-Tz-TCO-trastuzumab was also conducted and exhibited high tumor uptake (21.2 ± 5.6%ID/g 6 days post-injection) with low uptake in non-target tissues. Conclusions The novel platform shows promise as a multi-modal probe for theranostic applications. In particular, access to an advanced synthetic intermediate where tailored chelators can be incorporated in the last step of synthesis expands the potential use of the scaffold to other radiometals. Future studies including validation of ex vivo fluorescence imaging and exploiting the pre-targeting approach available through the IEDDA reaction are warranted.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Compounds Containing Polydentate Chelators'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles